Project Summary: Glioblastoma multiforme is a primary malignancy of the central nervous system that is nearly universally fatal due to the disseminated nature of these tumors. In this context, our lab and others have investigated unique tumor-tropic properties of neural stem cells (NSCs) as a novel platform for targeted delivery of anti-cancer agents in the brain. However, despite the strong tumor tropism exhibited by NSCs, only a small portion of the transplanted cells is able to migrate towards the tumor. This poor tumor homing efficiency is one of the limiting factors for NSC-based anti-cancer therapeutic approach and must be address. On this basis, I now propose to study the underlying molecular mechanisms of the inherent tumor-tropic properties of NSCs, which will allow us to develop protocol to further improve the tumor homing efficiency of NSCs. Our preliminary data indicated that migratory subpopulation of NSCs differs significantly from their nonmigratory counterpart based on the level of VEGFR2 and nestin expression. Moreover, blocking VEGFR2/VEGF signaling significantly impaired tumor-tropic migratory properties of NSCs. Thus, further detail understanding of signaling pathways that regulate migratory properties of NSCs will be crucial for development of optimized NSC-based targeted therapy (Aim 1). In addition, the reported immunosuppressive properties of NSCs are a very attractive attribute to their utilization as a cell carrier for novel anti-glioma therapy given that they will allow therapeutic payloads such as oncolytic viruses to be shielded from the host immune response. Therefore, I now propose to characterize the molecular nature of NSC-mediated immunosuppressant in the context of viral infection and examine how it may help to enhance therapeutic efficacy of anti-glioma oncolytic virotherapy (Aim 2). And finally, our preliminary data show that the viability of NSCs is significantly compromised upon ex vivo loading with the oncolytic virus due to replication-mediated carrier cell lysis. This is an essential step for the tumor-specific amplification of the therapeutic viruses, but counter-intuitive for long-term survival and tumor-specific homing of the carrier cells. Based on this, I hypothesize that blocking viral replication transiently during ex vivo loading will enhance the survival, loading capacity and tropism of NSCs for gliomas. In our final specific aim, I now propose to develop an inducible system that will allow us to maximize the ex vivo loading of the oncolytic virus without altering the survival and tropism of the NSCs (Aim 3). In conclusion, the proposed studies have the potential to making an impact beyond neuro-oncology and will accelerate the translational of the stem cell-based therapy in the clinic.